linux-stable.git/fs/fs-writeback.c, branch v4.16

writeback: update comment in inode_io_list_move_locked

2018-01-06T16:18:00+00:00

The @head can be wb->b_dirty_time, so update the comment.

Acked-by: Tejun Heo 
Signed-off-by: Wang Long 
Signed-off-by: Jens Axboe

Rename superblock flags (MS_xyz -> SB_xyz)

2017-11-27T21:05:09+00:00

This is a pure automated search-and-replace of the internal kernel
superblock flags.

The s_flags are now called SB_*, with the names and the values for the
moment mirroring the MS_* flags that they're equivalent to.

Note how the MS_xyz flags are the ones passed to the mount system call,
while the SB_xyz flags are what we then use in sb->s_flags.

The script to do this was:

    # places to look in; re security/*: it generally should *not* be
    # touched (that stuff parses mount(2) arguments directly), but
    # there are two places where we really deal with superblock flags.
    FILES="drivers/mtd drivers/staging/lustre fs ipc mm \
            include/linux/fs.h include/uapi/linux/bfs_fs.h \
            security/apparmor/apparmorfs.c security/apparmor/include/lib.h"
    # the list of MS_... constants
    SYMS="RDONLY NOSUID NODEV NOEXEC SYNCHRONOUS REMOUNT MANDLOCK \
          DIRSYNC NOATIME NODIRATIME BIND MOVE REC VERBOSE SILENT \
          POSIXACL UNBINDABLE PRIVATE SLAVE SHARED RELATIME KERNMOUNT \
          I_VERSION STRICTATIME LAZYTIME SUBMOUNT NOREMOTELOCK NOSEC BORN \
          ACTIVE NOUSER"

    SED_PROG=
    for i in $SYMS; do SED_PROG="$SED_PROG -e s/MS_$i/SB_$i/g"; done

    # we want files that contain at least one of MS_...,
    # with fs/namespace.c and fs/pnode.c excluded.
    L=$(for i in $SYMS; do git grep -w -l MS_$i $FILES; done| sort|uniq|grep -v '^fs/namespace.c'|grep -v '^fs/pnode.c')

    for f in $L; do sed -i $f $SED_PROG; done

Requested-by: Al Viro 
Signed-off-by: Linus Torvalds

writeback: merge try_to_writeback_inodes_sb_nr() into caller

2017-10-10T14:14:37+00:00

Since commit 925a6efb8ff0c ("Btrfs: stop using
try_to_writeback_inodes_sb_nr to flush delalloc") this function hasn't
been used outside so stop exporting it.

In addition we merge it into try_to_writeback_inodes_sb() which is the
only caller.  Also change return type of try_to_writeback_inodes_sb to
void as the only user ext4 doesn't care.

Reviewed-by: Jan Kara 
Signed-off-by: Rakesh Pandit 
Signed-off-by: Jens Axboe

writeback: eliminate work item allocation in bd_start_writeback()

2017-10-04T17:24:12+00:00

Handle start-all writeback like we do periodic or kupdate
style writeback - by marking the bdi_writeback as needing a full
flush, and simply waking the thread. This eliminates the need to
allocate and queue a specific work item just for this purpose.

After this change, we truly only ever have one of them running at
any point in time. We mark the need to start all flushes, and the
writeback thread will clear it once it has processed the request.

Reviewed-by: Jan Kara 
Signed-off-by: Jens Axboe

writeback: only allow one inflight and pending full flush

2017-10-03T14:38:17+00:00

When someone calls wakeup_flusher_threads() or
wakeup_flusher_threads_bdi(), they schedule writeback of all dirty
pages in the system (or on that bdi). If we are tight on memory, we
can get tons of these queued from kswapd/vmscan. This causes (at
least) two problems:

1) We consume a ton of memory just allocating writeback work items.
   We've seen as much as 600 million of these writeback work items
   pending. That's a lot of memory to pointlessly hold hostage,
   while the box is under memory pressure.

2) We spend so much time processing these work items, that we
   introduce a softlockup in writeback processing. This is because
   each of the writeback work items don't end up doing any work (it's
   hard when you have millions of identical ones coming in to the
   flush machinery), so we just sit in a tight loop pulling work
   items and deleting/freeing them.

Fix this by adding a 'start_all' bit to the writeback structure, and
set that when someone attempts to flush all dirty pages. The bit is
cleared when we start writeback on that work item. If the bit is
already set when we attempt to queue !nr_pages writeback, then we
simply ignore it.

This provides us one full flush in flight, with one pending as well,
and makes for more efficient handling of this type of writeback.

Acked-by: Johannes Weiner 
Tested-by: Chris Mason 
Reviewed-by: Jan Kara 
Signed-off-by: Jens Axboe

writeback: move nr_pages == 0 logic to one location

2017-10-03T14:38:17+00:00

Now that we have no external callers of wb_start_writeback(), we
can shuffle the passing in of 'nr_pages'. Everybody passes in 0
at this point, so just kill the argument and move the dirty
count retrieval to that function.

Acked-by: Johannes Weiner 
Tested-by: Chris Mason 
Reviewed-by: Jan Kara 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

writeback: make wb_start_writeback() static

2017-10-03T14:38:17+00:00

We don't have any callers outside of fs-writeback.c anymore,
make it private.

Acked-by: Johannes Weiner 
Tested-by: Chris Mason 
Reviewed-by: Jan Kara 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

writeback: provide a wakeup_flusher_threads_bdi()

2017-10-03T14:38:17+00:00

Similar to wakeup_flusher_threads(), except that we only wake
up the flusher threads on the specified backing device.

No functional changes in this patch.

Acked-by: Johannes Weiner 
Tested-by: Chris Mason 
Reviewed-by: Jan Kara 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

writeback: remove 'range_cyclic' argument for wb_start_writeback()

2017-10-03T14:38:17+00:00

All the callers pass in 'true' for range_cyclic, so kill the
argument.

Signed-off-by: Jens Axboe

writeback: switch wakeup_flusher_threads() to cyclic writeback

2017-10-03T14:38:17+00:00

We're writing back the full range of dirty pages on the devices,
there's no point in making this special and not do normal range
cyclic writeback.

Reviewed-by: Jan Kara 
Signed-off-by: Jens Axboe